Seller responsible for payment broken window during inspection?

We have a problem with the house that we bought last August that we need assistance with. During the inspection on the day of purchase, the seller tried to show how to open a difficult window, and during that demonstration, the window broke. It can now no longer be opened, closed, or secured. The seller's real estate agent was there, and we also had a real estate agent present advising us. When I asked whether this could be put on the inspection form, our agent said that we could sort it out with the seller later. When we asked the real estate agent and our mortgage broker what we should do, they said we should get two quotes and then send them. It took quite some time to get quotes for window repairs due to the business of workmen (approximately 2000 Eur.) When we contacted the seller yesterday via Whatsapp (written) he indicated that we had waited too long and he was no longer responsible for this expense. We disagree strongly. What can we do? The seller's real estate agent is not a registered agent. We do not have the seller's address.